Optical/electrical transducer using semiconductor nanowire wicking structure in a thermal conductivity and phase transition heat transfer mechanism

ABSTRACT

An optical/electrical transducer device has housing, formed of a thermally conductive section and an optically transmissive member. The section and member are connected together to form a seal for a vapor tight chamber. Pressure within the chamber configures a working fluid to absorb heat during operation of the device, to vaporize at a relatively hot location as it absorbs heat, to transfer heat to and condense at a relatively cold location, and to return as a liquid to the relatively hot location. The transducer device also includes a wicking structure mounted within the chamber to facilitate flow of condensed liquid of the working fluid from the cold location to the hot location. At least a portion of the wicking structure comprises semiconductor nanowires, configured as part of an optical/electrical transducer within the chamber for emitting light through and/or driven by light received via the transmissive member.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/221,050, filed Aug. 30, 2011 entitled “OPTICAL/ELECTRICAL TRANSDUCERUSING SEMICONDUCTOR NANOWIRE WICKING STRUCTURE IN A THERMAL CONDUCTIVITYAND PHASE TRANSITION HEAT TRANSFER MECHANISM,” the entire contents ofwhich are incorporated herein by reference.

This application is related to U.S. patent application Ser. No.13/221,244 filed Aug. 30, 2011 entitled “THERMAL CONDUCTIVITY AND PHASETRANSITION HEAT TRANSFER MECHANISM INCLUDING OPTICAL ELEMENT TO BECOOLED BY HEAT TRANSFER OF THE MECHANISM.”

This application is related to U.S. patent application Ser. No.13/221,083 filed Aug. 30, 2011 entitled “PHOSPHOR INCORPORATED IN ATHERMAL CONDUCTIVITY AND PHASE TRANSITION HEAT TRANSFER MECHANISM.”

BACKGROUND

Many different types of active optical elements for emitting orresponding to light used in optical/electrical transducers requireeffective dissipation of heat. Consider a semiconductor light emitter,such as a light emitting diode (LED) or laser diode, as a first example.To generate more light, the device is driven harder by a higher powerdrive current. However, the device then generates more heat.

The semiconductor may be damaged or break down if healed to or above acertain temperature. If the temperature gets too high, the device mayburn out instantly. All semiconductor light emitters decline inefficiency of light generation as they are operated over time. However,even if the temperature is not high enough to burn out the devicequickly, operating a semiconductor light emitter at relatively hightemperatures (but below the burn-out temperature) for an extended periodwill cause the semiconductor light emitter to degrade more quickly thanif operated at lower temperatures. Even when a device is running withinits rated temperature, the hotter it gets, the less efficient itbecomes. Conversely, the cooler the device operates, the more efficientit is.

Many available types of LEDs fail at ˜150° C. LED performance datatypically is based on junction temperature of 25° C. However, at moretypical junction temperatures (˜100° C.), operating performance isdegraded by ˜20% from the specified performance data.

As a solid state light emitter device such as a LED operates, thesemiconductor generates heat. The heat must be effectively dissipatedand/or the electrical drive power (and thus light output) must be keptlow enough, to avoid breakdown or rapid performance degradation and/orto maintain operating efficiency. The package or enclosure of thesemiconductor light emitter device typically includes a heat slug of ahigh thermal conductivity, which is thermally coupled to the actualsemiconductor that generates the light. In operation, the slug isthermally coupled to a cooling mechanism outside the device package,such as a heat pipe and/or a heat sink. External active cooling may alsobe provided.

To increase the intensity of the light generated, the semiconductorlight emitter may be driven with a higher intensity electrical current.Alternatively, an overall system or lighting device may include a numberof semiconductor light emitters which together can produce a desiredquantity of light output. With either approach, the increase inintensity of generated light increases the amount of heat that needs tobe dissipated to avoid breakdown or rapid performance degradation and/orto maintain operating efficiency.

The examples above relate to light generation devices or systems.However, similar heat dissipation issues may arise in devices or systemsthat convert light to other forms of energy such as electricity. Forexample light sensors or detectors and/or photovoltaic devices maydegrade or breakdown if overheated, e.g. if subject to particularlyintense input light of if subject to high light input over extended timeperiods. Even when a device is running within its rated temperature, thehotter it gets, the less efficient it becomes. Conversely, the coolerthe device operates, the more efficient it is.

For these and other types of active optical elements for emitting orresponding to light, there is a continuing need for ever more effectivedissipation of heat. Improved heat dissipation may provide a longeroperating life for the active optical element. Improved heat dissipationmay allow a light emitter to be driven harder to emit more light orallow a detector/second or photovoltaic to receive and process moreintense light.

Many thermal strategies have been tried to dissipate heat from and coolactive optical elements. Many systems or devices that incorporate activeoptical elements use a heat sink to receive and dissipate heat from theactive optical element(s). A heat sink is a component or assembly thattransfers generated heat to a lower temperature medium. Although thelower temperature medium may be a liquid, the lower temperature mediumoften is air.

A larger heat sink with more surface area dissipates more heat to theambient atmosphere. However, there is often a tension or trade offbetween the size and effectiveness of the heat sink versus thecommercially viable size of the device that must incorporate the sink.For example, if a LED based lamp must conform to the standard formfactor of an A-lamp, that form factor limits the size of the heat sink.To improve thermal performance for some applications, an active coolingelement may be used, to dissipate heat from a heat sink or from anotherthermal element that receives heat from the active optical element(s).Examples of active cooling elements include fans, Peltier devices,membronic cooling elements and the like.

Other thermal strategies for equipment that use active optical elementshave utilized heat pipes or other devices based on principles of athermal conductivity and phase transition heat transfer mechanism. Aheat pipe or the like may be used alone or in combination with a heatsink and/or an active cooling element.

A device such as a heat pipe relies on thermal conductivity and phasetransition between evaporation and condensation to transfer heat betweentwo interfaces. Such a device includes a vapor chamber and working fluidwithin the chamber, typically at a pressure somewhat lower thanatmospheric pressure. The working fluid, in its liquid state, contactsthe hot interface where the device receives heat input. As the liquidabsorbs the heat, it vaporizes. The vapor fills the otherwise emptyvolume of the chamber. Where the chamber wall is cool enough (the coldinterface), the vapor releases heat to the wall of the chamber andcondenses back into a liquid. Thermal conductivity at the cold interfaceallows heat transfer away from the mechanism, e.g. to a heat sink or toambient air. By gravity or a wicking structure, the liquid form of thefluid flows back to the hot interface. In operation, the working fluidgoes through this evaporation, condensation and return flow to form arepeating thermal cycle that effectively transfers the heat from the hotinterface to the cold interface. Devices like heat pipes can be moreeffective than passive elements like heat sinks, and they do not requirepower or mechanical parts as do active cooling elements. It is best toget the heat away from the active optical element as fast as possible,and the heat pipe improves heat transfer away from the active opticalelement, even where transferring the heat to other heat dissipationelements.

Although these prior technologies do address the thermal issuessomewhat, there is still room for further improvement.

For example, passive cooling elements, active cooling elements and heattransfer mechanisms that rely on thermal conductivity and phasetransition have been implemented outside of the devices that incorporateactive optical elements. A light processing device may include one ormore elements coupled to the actual active optical element to transferheat to the external thermal processing device. In our LED example, heatpasses through of the layers of the semiconductor, to the heat slug andthen to the external thermal processing device(s). The need to transferthe heat through so many elements and the various interfaces betweenthose elements reduces efficiency in cooling the thermally susceptiblecomponent(s) of the active optical element. Again referencing the LEDexample, the need to transfer the heat through so many elements reducesefficiency in cooling the LED chip, particularly cooling at the internalthe layer/point in the semiconductor chip where the light is actuallygenerated.

It has been suggested that a heat pipe type mechanism could beincorporated at the package level with the LED (WO 2007/069119 (A1)).However, even in that device, a heat spreader and a light transmissivecollimator encapsulate the actual LED chip and separate the chip fromthe working fluid. Heat from the LED chip structure is transferredthrough the heat spreader to the working fluid much like the priorexamples that used an external heat pipe coupled to the heat slug of theLED package.

There is an increasing desire for higher, more efficient operation(light output or response to light input) in ever smaller packages. Asoutlined above, thermal capacity is a limiting technical factor. Thermalcapacity may require control of heat at the device level (e.g.transducer package level and/or macro device level such as in a lamp orfixture).

Hence, it may be advantageous to reduce the distance and/or numberelements and interfaces that the heat must pass through from the activeoptical element. Also, improvement in technologies to more effectivelydissipate heat from active optical elements may help to meet increasingperformance demands with respect to the various types of equipment thatuse the active optical elements.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing figures depict one or more implementations in accord withthe present teachings, by way of example only, not by way of limitation.In the figures, like reference numerals refer to the same or similarelements.

FIG. 1 is a cross-sectional view of an example of an optical/electricaltransducer apparatus, in the form of a thermal conductivity and phasetransition heat transfer mechanism that incorporates a semiconductortransducer utilizing semiconductor nanowires that also form at least aportion of the wicking structure of the thermal conductivity and phasetransition heat transfer mechanism.

FIG. 2 is an enlarged detailed view of a portion of the semiconductortransducer in the apparatus of FIG. 1, including a number of thesemiconductor nanowires.

FIG. 3 is an enlarged detailed view of a portion of the thermallyconductive part of the housing and associated part of the wickingstructure, of the combined phase transition heat transfer mechanism ofFIG. 1, showing phosphor bearing nanowires.

FIG. 4 is an enlarged detailed view of a portion of the thermallyconductive part of the housing and associated part of the wickingstructure, of the combined phase transition heat transfer mechanism ofFIG. 1, showing metal nanowires.

FIG. 5 is a comparative diagram useful in explaining how reducing thesize and increasing the number of thermal elements per unit areaincreases the surface area for heat transfer and reduces the thermalresistance, and thus shows the advantages of using nanowires orsimilarly sized elements in the wicking structure of the thermalconductivity and phase transition heat transfer mechanism of anoptical/electrical transducer apparatus.

FIG. 6 is a cross-sectional view of an example of an optical/electricaltransducer apparatus, where the semiconductor transducer, such as a LEDor photodiode, utilizes semiconductor nanowires that also form a portionof the wicking structure.

FIGS. 7 and 8 are top and isometric views of a light emitting typeoptical/electrical transducer apparatus and heat sink as may be used ina fixture or lamp/light bulb.

FIG. 9A is a cross-sectional view taken along line A-A of FIG. 7.

FIG. 9B is an enlarged detail view of a portion of theoptical/electrical transducer apparatus and heat sink of FIG. 9A.

FIGS. 10 and 11 are top and isometric views of another light emittingtype optical/electrical transducer apparatus and heat sink as may beused in a fixture or lamp/light bulb.

FIG. 12A is a cross-sectional view taken along line A-A of FIG. 10.

FIG. 12B is an enlarged detail view of a portion of theoptical/electrical transducer apparatus and heat sink of FIG. 12A,showing the addition of a phosphor layer.

FIGS. 13 and 14 are top and isometric views of a light receiving typeoptical/electrical transducer apparatus, a heat sink and a lightconcentrator, as may be used in for a sensor or photovoltaic apparatus.

FIG. 15A is a cross-sectional view taken along line A-A of FIG. 13.

FIG. 15B is an enlarged detail view of a portion of theoptical/electrical transducer apparatus and heat sink of FIG. 15A.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant teachings. However, it should be apparent to those skilledin the art that the present teachings may be practiced without suchdetails. In other instances, well known methods, procedures, components,and/or circuitry have been described at a relatively high-level, withoutdetail, in order to avoid unnecessarily obscuring aspects of the presentteachings.

The various technologies disclosed herein relate to apparatuses, devicesor systems in which the semiconductor of an optical/electricaltransducer takes the form of semiconductor nanowires. The nanowires ofthe transducer also are part of the internal wicking structure of athermal conductivity and phase transition heat transfer mechanism thatincorporates the transducer. A variety of examples of such arrangementsas well as techniques for making and operating such transducers arediscussed below. An optical/electrical transducer apparatus is a devicethat converts between forms of optical and electrical energy, forexample, from optical energy to an electrical signal or from electricalenergy to an optical output. Examples of optical-to-electricaltransducers include various sensors, photovoltaic devices and the like.Examples of electrical-to-optical transducers include various lightemitters, although the emitted light may be in the visible spectrum orin other wavelength ranges.

At a high level, an exemplary optical/electrical transducer apparatusincludes a housing having a section that is thermally conductive and amember that is at least partially optically transmissive. The opticallytransmissive member is connected to the thermally conductive section ofthe housing to form a seal for a vapor tight chamber enclosed by thesection and the member that together form the housing, although themember does allow passage of optical energy into and/or out of theapparatus. The exemplary apparatus also includes a working fluid withinthe chamber. The pressure within the chamber configures the workingfluid to absorb heat during operation of the apparatus, to vaporize at arelatively hot location as it absorbs heat, to transfer heat to andcondense at a relatively cold location, and to return as a liquid to therelatively hot location. The exemplary apparatus also includes a wickingstructure mounted within the chamber to facilitate flow of the condensedliquid of the working fluid from the cold location to the hot locationof the mechanism. At least a portion of the wicking structure comprisessemiconductor nanowires. The semiconductor nanowires are configured asat least part of an optical/electrical transducer within the chamber,for emitting light through and/or driven by light received via thetransmissive member.

At least some surfaces of the semiconductor nanowires directly contactthe working fluid for heat transfer. The phase transition heat transfervia the thermal cycle of the working fluid more efficiently transfersheat produced during operation of the transducer from the semiconductornanowires at or near the hot location to the cold location. For example,the semiconductor nanowires are part of the wicking structure, portionsof the nanowires are directly exposed to the working fluid, without anyadditional intervening members, layers or interfaces that mightotherwise impede the transfer of heat from the transducer to the workingfluid. The improved efficiency of the heat transfer and dissipation viathe thermal conductivity and phase transition heat transfer mechanismmay improve the operations and/or operation life of the semiconductortransducer. For example, it may be possible to operate the coolertransducer at higher light intensity or higher electrical power withoutadverse impact on the performance and/or life of the transducer.

Reference now is made in detail to the examples illustrated in theaccompanying drawings and discussed below. FIG. 1 is a cross-sectionalview of a somewhat stylized example of an optical/electrical transducerapparatus 1, where the actual transducer is an active optical element 17of or within a combined phase transition heat transfer mechanism. Anactive optical element converts energy from one form or another by anelectrical process and/or an excitation state change process, where atleast one form of the energy is optical, e.g. light. Active opticalelements include optically driven elements, such as optically pumpedphosphors and/or electrical devices driven by light to produceelectricity, as well as electrical devices and/or phosphors driven byelectricity or electrical/electromagnetic fields to produce light. Inthe example, the active optical element 17 is a semiconductor“transducer” for converting between light and electricity that, at leastin part, uses semiconductor nanowires 19 to produce or respond to light.The nanowires 19 are also part of a wicking structure 15. By contrast,passive optical elements process and even change the character of light,but by optical processing only, that is to say without use of anelectrical and/or excitation state change process. Examples of passiveoptical elements include windows, lenses, optical color filters,reflectors, gratings, diffusers, and the like.

The transducer apparatus 1 includes a housing 3. The housing 3 has atleast one section that is thermally conductive. In the example of FIG.1, the major section 5 of the housing 3 is formed of a thermallyconductive material. Examples of suitable materials include metals, suchas copper and aluminum, although other thermally conductive materials,such as thermally conductive plastics and ceramics, may be used to formthe housing section 5. A portion of the housing section 5 will form acold location 7, for example, acting as or coupled to a heat sink (notseparately shown).

The housing 3 has a member 9 that is at least partially opticallytransmissive. The member 9 may be transparent or translucent or exhibitother transmissive characteristics (e.g. non-white color filtering),depending on the optical requirements of the particular application ofthe transducer apparatus 1. The material forming the member 9 may be anymaterial of sufficient optical transmissivity and desired colorcharacteristic for the particular application that is also able towithstand the expected operating temperatures of the transducerapparatus 1. Examples of suitable materials for the member 9 includevarious forms of glass, ceramics and plastics. The material for themember 9 may or may not need to be heat resistant, depending on theoperating temperature at the hot location 7 maintained by operation ofthe thermal conductivity and phase transition heat transfer mechanism.The optically transmissive member 9 is connected to the housing section5 to form a seal for a vapor tight chamber 11 enclosed by the thermallyconductive housing section 5 and the optically transmissive member 9.The material of the member 9 is sufficiently transmissive to light, atleast in the portion of the optical energy spectrum that is relevant tooperations of the apparatus 1, so as to allow passage of optical energyinto and/or out of the apparatus 1.

As noted, the optically transmissive member 9 is attached to the housingsection 5 to form a seal for a vapor tight chamber 11. For example, ifthe optically transmissive member 9 is a glass or ceramic material andthe housing section 5 is formed of a metal, the two elements may bejoined by a glass frit process or by application of a suitable epoxy.

The exemplary apparatus 1 also includes a working fluid within thechamber 11. The pressure within the chamber 11, typically a pressuresomewhat lower than atmospheric pressure, configures the working fluidto absorb heat during operation of the apparatus, to vaporize at arelatively hot location 13 as it absorbs heat, to transfer heat to andcondense at the relatively cold location 7, and to return as a liquid tothe relatively hot location. A variety of different fluids may be usedas the working fluid, and the pressure is determined based on the fluidtype and the amount of heat that the fluid is expected to transfer.

The working fluid, in its liquid state, contacts the hot interface atthe location 13 where the apparatus receives or produces heat. In theexample, heat is absorbed from surfaces of the semiconductor nanowires19 of the transducer element 17. As the liquid absorbs the heat, itvaporizes. The vapor fills the otherwise empty volume of the chamber 11.Where the chamber wall is cool enough (the cold interface at location7), the vapor releases heat to the wall of the chamber 11 and condensesback into a liquid. The drawing shows a central arrow from the hotlocation 13 toward the cold location 7. This arrow generally representsthe flow of heat in the vapor state of the working fluid from the hotlocation 13 where the working fluid vaporizes toward the cold location 7where the working fluid transfers heat for output via the thermallyconductive housing section 5 and condenses back to the liquid form. Theliquid form of the fluid flows back to the hot interface at location 13.The drawing shows arrows generally along the outer wall(s) of thehousing from the relatively cold location 7 back to the relatively hotlocation 13. The arrows generally represent the flow of the condensedworking fluid from the relatively cold location 7 back to the relativelyhot location 13 where the fluid again vaporizes as it absorbs heat. Inoperation, the working fluid goes through this evaporation, condensationand return flow to form a repeating thermal cycle that effectivelytransfers the heat from the hot interface at location 13 to the coldinterface at location 7.

The apparatus 1 thus is configured as a thermal conductivity and phasetransition heat transfer mechanism, similar to many mechanisms which aresometimes referred to as “heat pipes.” The thermal conductivity of thehousing section 5 and the phase transition cycle through evaporation andcondensation transfer heat from the hot location 13 to the cold location7. Thermal conductivity at the cold interface allows heat transfer awayfrom the mechanism, e.g. to a heat sink or to ambient air. Activecooling may also be provided. The configuration of the mechanismtogether with the degree of cooling determines the internal operatingtemperature. For example, the mechanism and a heat sink may support amaximum internal operating temperature around 50° C. Addition of activecooling or refrigeration at the cold interface may enable operation at amuch lower internal temperature, such as 0° C.

The exemplary apparatus 1 also includes a wicking structure 15 mountedwithin the chamber 11 to facilitate flow of the condensed liquid of theworking fluid from the cold location 7 to the hot location 13 of themechanism 1. Capillary action or “wicking” relies on inter-molecularforces between a liquid and the surface(s) of a material around theliquid to cause movement of the liquid along or through the material.This action can overcome other forces on the liquid, such as gravity, topromote a desired movement of the liquid. In the thermal conductivityand phase transition heat transfer mechanism, the wicking structure 15promotes movement of the condensed liquid back from the cold location 7to the hot location 13.

The wicking structure 15 may take many forms, such as sintered metal,phosphor, glass or ceramic powder; woven copper; surface grooves, mesharrangements or small closely spaced wires extending inward from thesurfaces of the housing forming the walls of the chamber 11; as well asnano-scale wire structures extending inward from the chamber surface(s);and various combinations of these forms. The spacing between elements ofthe wicking structure 15 is sufficiently small to cause inter-molecularforces on the liquid form of the working fluid to cause the liquid toflow toward the region where the fluid vaporizes, that is to say, thehot location 13 in the apparatus 1. This wicking or capillary actionenables the liquid form of the working fluid to flow back to the hotlocation 13 regardless of the orientation of (and thus the impact ofgravity on fluid in) the heat transfer mechanism.

The apparatus 1 includes an active optical element 17. In this case, theactive optical element is an optical/electrical transducer. Thetransducer 17 converts between optical and electrical energy. Thepresent teachings apply to transducers 17 for emitting light in responseto an electrical drive signal or for receiving and responding to lightto produce an electrical signal. In the apparatus 1, light enters theapparatus through the optically transmissive member 9, for anoptical-to-electrical conversion application to reach the transducer 17.For an electrical-to-optical conversion application, light produced byoperation of the transducer 17 emerges from the apparatus 1 through theoptically transmissive member 9.

If the apparatus 1 is cylindrical, then when viewed from either end, theapparatus 1 would appear circular. The member 9 could be circular orhave other shapes, even in a cylindrical implementation of the apparatus1. Those skilled in the art will appreciate that the lateral shapes ofthe mechanism as a whole and of the optically transmissive member maytake other geometric forms, such as oval, rectangular or square, just toname a few examples.

The orientation in the drawing, in which light enters the apparatus 1 oris emitted from the apparatus 1 to the left in directions about asomewhat horizontal central axis, is shown only for purposes ofillustration. Those skilled in the art will appreciate that theapparatus may be used in any other orientation that is desirable orsuitable for any particular application of the transducer apparatus.Some implementations may utilize more than one optically transmissivemember, to facilitate receipt or emission of light in additionaldirections. Although not shown, passive optical processing elements,such as diffusers, reflectors, lens and the like, may be coupled to theoptically transmissive member to process light directed into thetransducer apparatus 1 or to process light emitted from the transducerapparatus 1.

The examples discussed herein relate to transducers 17 that are formedat least in part by semiconductor nanowires 19, and in an apparatus likethat of FIG. 1, the nanowires also serve as part of the wickingstructure for purposes of promoting the liquid flow in the phasetransition cycle of the heat transfer mechanism.

Hence, in the example of FIG. 1, the wicking structure 15 includes atleast two different portions 19 and 21. The portion of the wickingstructure 19 is formed of the semiconductor nanowires that also form atleast part of the actual optical/electrical transducer 17 within thechamber 11. The semiconductor transducer 17 that includes thesemiconductor nanowires 19 of the wicking structure 15 is configured toemit light through the optically transmissive member 9, and/or thesemiconductor transducer 17 that includes the semiconductor nanowires 19of the wicking structure is configured to be driven by light receivedvia the optically transmissive member 9.

FIG. 2 shows an example of a section of the optical/electricaltransducer 17, utilizing the semiconductor nanowire portion 19 of thewicking structure. As discussed herein, applicable semiconductor lightemitters essentially include any of a wide range light emitting orgenerating devices formed from organic or inorganic semiconductormaterials. Similarly, the present discussion encompasses any of a widerange of sensors, photovoltaics or other transducers for producing anelectrical signal in response to optical energy that may be formed fromorganic or inorganic semiconductor materials.

The active optical element, in this case the optical/electricaltransducer 17, includes a conductive base 25. The base may be formed ofan appropriate conductive material. For an arrangement like that of FIG.1, where the transducer 17 is adjacent to the optically transmissivemember 9, the conductive base 25 may also be optically transmissive. Forexample, the conductive base 25 can be formed of Indium Tin Oxide (ITO),other similar transparent conductive oxides, transparent conductingpolymers, or layers consisting of transparent carbon nanotubes. Thetransparent conductive base 25 could form the optically transmissivemember 9 of the apparatus housing 3, but in the example of FIGS. 1 and2, the conductive base 25 is a separate element or layer on or adjacentto the optically transmissive member 9 of the apparatus housing 3. IfITO or another similar transparent conductive oxide is used, forexample, the transparent conductive base 25 could take the form of alayer formed on a portion of the inner surface of the opticallytransmissive member 9. Although not separately shown, an electricalconnection will be provided to the base 25, to provide one of thecurrent path couplings to the semiconductor device of the actualtransducer 17.

The transducer also includes nanowires 19 grown to extend out from theconductive base 25. Nanowires are wire-like structures having nano-scalecross-sectional dimensions. Although the cross-section of a nanowire maynot be circular, it is often easiest to consider the lateral dimensionof the nanowire to be a diameter. An individual nanowire 27 thereforemay have an outer diameter measured in nanometers, e.g. in a range ofapproximately 1-500 nanometers. Hence, “nanowire” is meant to refer toany continuous wire or filament of indefinite length having an averageeffective diameter of nanometer (nm) dimensions. The “nanowire” term istherefore intended to refer to nanostructures of indefinite length,which may have a generally circular cross-sectional configuration or anon-circular cross-section (e.g. nanobelts having a generallyrectangular cross-section).

Each individual semiconductor nanowire 27 in the example includes aninner nanowire 29 as a core and an outer nanowire 31. The inner andouter nanowires are doped with different materials so as to be ofdifferent semiconductor types. In the example, the inner nanowire 29 isan N type semiconductor, and the outer nanowire 31 is a P typesemiconductor, although obviously, the types could be reversed. As aresult of the semiconductor growth and doping processes, there issemiconductor junction or intrinsic region 33 formed between the twosemiconductor type nanowires 29, 31. In the example, the materialforming the intrinsic region and the P type semiconductor also extendsover the inner surface(s) of the conductive base 25 between the N typeinner nanowires 29. Those skilled in the art will recognize that thedoping may be applied so as to essentially reverse the semiconductortypes, e.g. so that the inner core nanowire 29 is a P type semiconductorand the outer nanowire 31 is an N type semiconductor.

Although not shown, reflectors may be provided at the distal ends (awayfrom the base 25) of the semiconductor nanowires 27 to direct more ofthe light produced by the nanowire diodes back through the base 25 andthe light transmissive member 9.

FIG. 2 also illustrates some of the working fluid 35 of the phasetransition cycle of the heat transfer mechanism. The working fluid 35directly contacts the outer surface(s) of at least the nanowires 27 ofthe semiconductor transducer, so that the fluid 35 may efficientlyabsorb heat from the transducer 17 during operation of the transducer.As noted, the conductive base 25 provides one of the electricalconnections to the semiconductor nanowires 27, in this example, to the Ntype semiconductor inner nanowires 29. Although other types ofelectrical connections to the outer nanowires 31 could be provided, inthe example of FIG. 2, the electrical connection to the P typesemiconductor outer nanowires 31 is provided via the working fluid 35.To that end, the example uses a fluid 35 that is electricallyconductive. Although not shown, the apparatus of FIG. 1 would include aconductive connection to the working fluid, for example, via a conductorconnected to a metal forming the section 5 of the housing 3.

The semiconductor type optical/electrical transducer can provideconversion between optical and electrical energy or can provideconversion between electrical and optical energy. For anoptical-to-electrical energy conversion, such as in a sensor orphotovoltaic device, light energy applied to the semiconductor deviceproduces a voltage across the P-N junction at the intrinsic region 33 ofeach nanowire 27, which allows a current to flow through a circuit viathe conductive base 25 and the working fluid 35. For anelectrical-to-optical energy conversion, the inner and outer nanowirestogether form a light emitting diode. A voltage is applied to produce adrive current through the diode, via the conductive base 25 and theworking fluid 35. Application of a voltage at or above the diode turn-onthreshold, across the P-N junction at the intrinsic region 33, causeseach of each of the nanowires 27 to produce light.

The discussion of FIG. 2 focused on the semiconductor structure of thetransducer 17 within the chamber 11 and the transducer operation.However, the nanowires 27 also form part of the wicking structure 15 ofthe combined phase transition and heat transfer mechanism. The spacingbetween the nanowires 27 is sufficiently small so as to facilitatecapillary action on the working fluid 35, so that the nanowires 27 alsofunction as portion 19 of the wicking structure 15 in the apparatus 1 ofFIG. 1. Although the entire wicking structure 15 could be formed ofsemiconductor nanowires like the nanowires 27, the wicking structure 15in our example also includes a somewhat different portion 21. Theportion 21 of the wicking structure 15 may take many forms, as notedearlier, in this case, on the various inner surface of the section 5 ofthe housing 3.

FIGS. 3 and 4 show two specific examples of arrangements that may beused as some or the entire portion 21 of the wicking structure 15 in thetransducer apparatus 1 of FIG. 1. The example of FIG. 3 uses a wickingarrangement 21 a formed of nanowires 37. However, in the example of FIG.3, the nanowires 37 are formed of an optically luminescent material suchas a phosphor or phosphor bearing medium. The phosphor or medium may begrown as nanowires 37 extending inward into the interior of the chamber11 from the inner surface of the section 5 of the housing 3. By way ofan example, particles of suitable phosphor(s) may be dispersed in apolymer matrix, and the phosphor-polymer matrix is grown in the form ofnanowires. Examples of suitable polymers include epoxies and silicon. Abarrier layer of a few nanometers up to around a micron may be providedon the surface of the phosphor nanowires 37, so long at the barrierlayer does not substantially impede flow of light to or from thephosphor or flow of heat from the excited phosphor to the fluid. Thephosphor converts some of the optical energy within the chamber 11 fromenergy in one wavelength range (the excitation band of the phosphor) toanother somewhat different wavelength range. There may or may not besome overlap of the excitation and emission spectra of the phosphor.

In an optical-to-electrical transducer application, the phosphor mayconvert some energy in a wavelength range that the semiconductortransducer can not process to a wavelength range that the semiconductortransducer can process or can at least process more efficiently.Converted light produced by the phosphor nanowires will eventually reachthe semiconductor transducer within the chamber 11, and can then beprocessed more effectively by the transducer. Hence, the phosphorconversion may improve sensitivity of the transducer apparatus 1.

In an electrical-to-optical transducer application, the phosphor mayconvert some energy from the semiconductor light emitting transducerfrom a less desirable wavelength range (e.g. near or outside the visiblespectrum) to a more desirable wavelength range (e.g. to fill-in a gap inthe spectral characteristic of light produced by the emitter), toimprove efficiency of the transducer apparatus 1 and/or to improve thequality of the light output. In the electrical-to-light type opticaltransducer application, the phosphor receives light emitted by thesemiconductor transducer 17 that has not yet emerged from the apparatus1 via the optically transmissive member 9. If in sections of the chamber11 not at or near the member 9, the phosphor recycles such light andretransmits it within the chamber for eventual passage through thetransparent conductive base 25 and the optically transmissive member 9.

Instead of a phosphor wicking structure as in FIG. 3, the example ofFIG. 4 uses a metal nanowire wicking structure 21 b. In the example ofFIG. 4, metallic nanowires 39 of sufficient size and closeness tofunction as the wicking structure are grown so as to extend inward fromthe inner surface of the section 5 of the housing 3. In addition tosupporting the capillary wicking function, the nanowires 39 may helpsupport current flow to or from the conductive working fluid if thefluid is conductive. The nanowires 39 may also be reflective to reflectlight within the chamber back to the transducer and/or the opticallytransmissive member 9, so as to improve re-circulation of light withinthe chamber and thereby improve overall optical performance of theapparatus 1 of FIG. 1.

Although referred to as a phosphor, each nanowire may include one ormore phosphors of different types where the mix of phosphors is chosento promote a particular application of the apparatus 1. Anothermulti-phosphor approach might use a phosphor of one type in nanowires inone region of the chamber and a phosphor of another type in a differentregion of the chamber.

In both the examples of FIGS. 3 and 4, the working fluid may beconductive. Where an optical-luminescent function is desirable, theworking fluid 35 a may also be or include a phosphor or the like. Ifphosphor particles are contained in the fluid 35 a, the particlesurfaces may be exposed to the fluid or the particles may beencapsulated in a barrier layer of a few nanometers up to around amicron, so long at the barrier layer does not substantially impede flowof light to or from the phosphor or flow of heat from the excitedphosphor to the fluid medium. The phosphor in the working fluid 35 a mayenhance certain aspects of the apparatus performance in a manner similarto that discussed above relative to the phosphor of the nanowires 37 inthe example of FIG. 3.

The examples of FIGS. 3 and 4 relate to different nanowire arrangementsfor one or more portions of the wicking structure. In both cases, thesize and spacing of the nanowires would be such as to provide acapillary flow of the liquid form of the working fluid. The workingfluid 35 or 35 a would directly contact the outer surface(s) of therespective nanowires.

As outlined above, the examples of FIGS. 3 and 4 may utilize anoptically luminescent material such as a phosphor; and a number of thefurther examples discussed below likewise may utilize an opticallyluminescent material such as a phosphor. Terms relating to phosphor areintended to encompass a broad range of materials excited by opticalenergy of a first or ‘excitation’ band that re-generate light in asomewhat different second or ‘emission’ band. Examples of phosphors thatmay be used in various applications discussed herein include traditionalphosphors, such as rare-earth phosphors, as well as semiconductornanophosphors sometimes referred to as quantum dots or Q-dots and dopedsemiconductor nanophosphors. Those skilled in the art will alsoappreciate that phosphors of similar types and/or of different types,emitting light of different spectral characteristics, may be used incombination to facilitate particular transducer applications.

The use of nanowires in the wicking structure, particularly on thesemiconductor transducer 17 and/or or on the housing section 5 at thecold location 7, also improves heat transfer. In general, smaller morenumerous heat transfer elements at these locations present increasedsurface area for heat transfer to/from the working fluid and thereforerepresent decreased thermal resistance. FIG. 5 is a comparative diagramuseful in explaining how reducing the size and increasing the number ofthermal elements per unit area of the housing wall increases totalsurface area for heat transfer and reduces the thermal resistance, bothof which help to improve the rate of thermal transfer to/from theworking fluid contacting the thermal transfer elements, in this casecontacting the nanowires. It is believed that this comparison helpsdemonstrate and explain advantages of using nanowires or similarly sizedelements in the wicking structure of the combined phase transition heattransfer mechanism of an optical/electrical transducer apparatus.

For discussion purposes, the square under each identifier (A), (B) and(C) represents a 2 mm×2 mm section of an inner surface of the vaporchamber of a thermal conductivity and phase transition heat transfermechanism. However, the different examples (A), (B) and (C) havedifferent sizes and numbers of heat transfer elements extending into theinterior of the chamber. In the illustrated views, the heat transferelements appear as circles, representing the end view (from inside thevapor chamber) of cylindrical heat transfer elements. Cylindrical shapesare used here for ease of modeling, although as noted earlier, othershapes may be used. For purposes of this comparison, we will assume thatthe heat transfer elements are all formed of the same material in eachand every one of the three examples in FIG. 5.

The first example (A) has four pins of radius 0.25 mm (diameter of 0.5mm). The length of the pins L need not be specified for comparisonpurposes. The number 4 in the formulae for the example is the number ofpins. The volume of each pin is 2π times the radius-squared times thelength (L) of the pins. As shown, the total volume of the material ofthe four pins is 0.25²*2π*L*4, which equals 0.78 L. For purposes ofcalculation of the surface area, we will use the outer cylindricalsurface only (without including the end surfaces) to somewhat simplifythe calculations for the comparison. With that approach, the surfacearea of a cylindrical pin is the diameter times π; times the length.Hence, the total cylindrical outer surface area presented by the fourpins at (A) would be 0.5*π*L*4, which equals 6.2 L. The thermalresistance of each pin equals the pin radius times the thermalresistance R of the material from which the pins are formed. In theexample (A) in which the radius of the pins is 0.25 mm, the thermalresistance of each pin is 0.25*R.

The second example (B) has sixteen (16) pins of radius 0.125 mm(diameter of 0.250 mm) of the same length L as in the previous example.As shown, the total volume of the material of the sixteen pins is0.125²*2π*L*16, which again equals 0.78 L. Again, using only thecylindrical surface area for purposes of comparison (without includingthe end surfaces), the total cylindrical outer surface area presented bythe sixteen pins at (B) would be 0.25*π*L*16, which equals 12.5 L. Thisdecrease in size and increase in number of pins results in approximatelydoubling the surface area for heat transfer in comparison to example(A). The thermal resistance of each pin in example (B), equals 0.125*R,which is half the thermal resistance of example (A).

The use of nanowires in the wicking structure, particularly thesemiconductor transducer 17 and/or or on the housing section 5 at thecold location 7, increases both the surface area for heat transfer andreduces the thermal resistance of each heat transfer element. Increasedsurface area and decreased thermal resistance both contribute toimproved heat transfer. Example (C) in FIG. 5 represents a nanowireconfiguration in which the 2 mm×2 mm area of the chamber wall has9.9×10⁹ nanowires, where the radius of each nanowire is 5×10⁻⁶ mm (5nanometers) or the diameter of each nanowire is 10×10⁻⁶ mm (10nanometers).

As shown at (C), the total volume of the material of the nanowires is(5×10⁻⁶)²*2π*L*(9.9×10⁹), which again equals 0.78 L. Again, using onlythe cylindrical surface area for purposes of comparison (withoutincluding the end surfaces), the total cylindrical outer surface areapresented by the nanowires at (C) would be 10×10⁻⁶*π*L*9.9×10⁹, whichequals (3.1×10⁵)L, which is approximately 50,000 times more surface areafor heat transfer than in first example (A). The thermal resistance ofeach nanowire in example (C), equals (5×10⁻⁶)*R, which is approximately50,000 times lower than the thermal resistance of example (A).

Hence, the use of nanowires in the wicking structure at various pointsin the exemplary transducer apparatuses discussed herein improvesthermal transfer capabilities. At a hot location or interface, use ofnanowires improves transfer of heat to the working fluid. At a coldlocation, use of nanowires improves transfer of heat from the workingfluid to the cold interface, e.g. for transfer through the interface toa heat sink, active cooling element or ambient air.

The use of the nanowires also helps with the wicking action. As noted,inter-molecular forces between a liquid and the surface(s) of thewicking material around the liquid produce capillary action to move ofthe liquid form of the working fluid along or through the material.Increasing the surface area helps to increase the inter-molecular forceson the liquid form of the working fluid. Hence, use of nanowires as thewicking structure, with increased surface area as shown above, alsoincreases the strength of the capillary action of the wicking structureon the liquid form of the working fluid.

As noted earlier, a variety of different fluids may be used as theworking fluid. Different fluids are used in various transducer apparatusconfigurations to support the heat transfer function, and in many of theexamples, to serve as a carrier for phosphor and/or as a conductor. Forexamples of the transducer apparatus that do not use the fluid as acarrier for phosphor or as a conductor, fluids commonly used in priorheat pipes and the like may be used, particularly if sufficientlytransparent to allow any light passage that may be desirable in theparticular apparatus configuration. For a working fluid that would carrysemiconductor nano-phosphor as the phosphor, examples of suitable fluidsinclude acetone, methanol, ethanol and toluene. If the nano-phosphor iswell encapsulated, water may be on option. Toluene may be a preferredchoice for many phosphors, however, for cooler internal workingtemperatures, ethanol me be preferred. For a working fluid that wouldcarry rare-earth-phosphor, examples of suitable fluids include acetone,methanol ethanol and toluene, although here water may be a preferredchoice. For a working fluid that is also electrically conductive,examples of suitable fluids include salt water, ammonia and fluids fromthe class of transparent ionic liquids.

FIG. 6 is a cross-sectional view of an example of an optical/electricaltransducer apparatus 61, where the semiconductor transducer 77, such asa LED or a photodiode, utilizes semiconductor nanowires 79 that alsoform a portion of the wicking structure 75 of the thermal conductivityand phase transition heat transfer mechanism that is an integral part ofthe transducer apparatus 61.

The transducer apparatus 61 includes a housing 63. The housing 63 isformed of a metal section 65 and a light transmissive member 69. In thisexample, the metal section 65 supports the semiconductor transducer 77;and the light transmissive member 69 forms a curved cover or dome overbut separated from the emitting portions of the semiconductor transducer77. Viewed from above or below, the apparatus could be circular, oval,rectangular, square or the like. The metal of section 65 may bereflective, but it is not optically transmissive in this example. Theoptically transmissive member 69 of the housing 63 may be formed of amaterial that is also thermally conductive, although it may not be asthermally conductive as the metal of section 65.

The semiconductor transducer 77 is located at a roughly central area orregion of the metal section 65, in this example, and a hot location 73is formed in the area within the chamber where heat is produced byoperation of a semiconductor transducer 77.

One or more portions of the member 69 and/or section 65 provide one ormore relatively cold interfaces, similar to that at the cold location inthe example of FIG. 1. Although the apparatus functions at variousorientations, in the illustrated orientation, a cold interface orlocation would be formed at 67 along the surface of the curved opticallytransmissive member 69 of the housing 63, although there may be othercold locations 67 within the chamber. The materials of the housingsection 65 and member 69 may be similar to those of the section 5 andthe member 9 in the example of FIG. 1, although other suitable materialsmay be used.

As in the earlier example, the optically transmissive member or section69 is attached to the housing section 65 to form a seal for a vaportight chamber 71. For example, if the optically transmissive member orsection 69 is a glass or ceramic material and the housing section 65 isformed of a metal, the two elements may be joined by a glass fritprocess or by application of a suitable epoxy.

The exemplary apparatus 61 also includes a working fluid within thechamber 71. Again, the pressure within the chamber 71, typically apressure somewhat lower than atmospheric pressure, configures theworking fluid to absorb heat during operation of the apparatus, tovaporize at the relatively hot location 73 as it absorbs heat from thetransducer 77, to transfer heat to and condense at the relatively coldlocation(s) 67, and to return as a liquid to the relatively hot location73. A variety of different fluids may be used as the working fluid, andthe pressure is determined based on the fluid type and the amount ofheat that the fluid is expected to transfer.

The working fluid, in its liquid state, contacts the hot interface atthe location 73 where the apparatus receives or produces heat. Forexample, the working fluid directly contacts the outer surfaces of thenanowires 79. As the liquid absorbs the heat, it vaporizes. The vaporfills the otherwise empty volume of the chamber 71. Where the chamberwall is cool enough (the cold interface at one or more locations 67),the vapor releases heat to the wall of the chamber 71 and condenses backinto a liquid. The liquid form of the fluid flows back to the hotinterface at location 73. In operation, the working fluid goes throughthis evaporation, condensation and return flow to form a repeatingthermal cycle that effectively transfers the heat from the hot interfaceto the cold interface.

Hence, as in the earlier example, the apparatus 61 is configured as athermal conductivity and phase transition heat transfer mechanism. Thethermal conductivity of the housing 63 and the phase transition cyclethrough evaporation and condensation transfer heat from the hot location73 to the cold locations 67.

As noted, the exemplary apparatus 61 also includes a wicking structure75 mounted within the chamber 71 to facilitate flow of condensed liquidof the working fluid from the cold locations 67 to the hot location 73of the mechanism. The capillary action of the wicking structure 75 canovercome other forces on the liquid, such as gravity, to promote adesired movement of the liquid, regardless of the orientation of theoptical/electrical transducer apparatus 61. The wicking structure maytake many forms, as outlined in the discussion of the earlier examples.

As in the earlier example, the apparatus 61 includes a semiconductortype optical/electrical transducer 77 for converting between optical andelectrical energy. The transducer in the example here is a diode,although the diode may be a light emitting diode or a photodiode. For animplementation using a photodiode form of the transducer 77, lightenters the apparatus 61 through the optically transmissive member 69,impacts on the photodiode transducer 77 and causes the diode to generatea responsive electrical signal. For an electrical-to-optical conversionapplication, a drive current is applied to the light emitting diode ofthe transducer 17 causing it to generate light, which emerges from theapparatus 61 through the optically transmissive member 69.

The orientation in the drawing, in which light enters the apparatus 61or is emitted from the apparatus 61 to/from directions above thehorizontal plane, is shown only for purposes of illustration. Thoseskilled in the art will appreciate that the apparatus 61 may be used inany other orientation that is desirable or suitable for any particularapplication of the transducer apparatus. As in the earlier example,optical processing elements (not shown), such as diffusers, reflectors,lens and the like, may be coupled to the optically transmissive member69 to process light directed into the transducer apparatus 61 or toprocess light emitted from the transducer apparatus 61.

The transducer 77 may be formed in a manner similar to that of thetransducer 17 in the examples of FIGS. 1 and 2, e.g. in the form of aconductive base with a semiconductor structure formed on the conductivebase. The semiconductor structure in turn includes semiconductornanowires, in the example of FIG. 6, nanowires 79. In this example, theconductive base can be a metal or an appropriately doped semiconductivematerial. Unlike the earlier example of FIG. 2, the conductive base neednot be transparent.

A first electrical connection path to the semiconductor structure of thetransducer 77 is provided via the conductive base. The outer surfaces ofthe semiconductor structure of the transducer 77, including the outersurfaces of the semiconductor nanowires 79, can be coated with atransparent conductor like one of those discussed earlier, in this case,to provide a second electrical connection path to the semiconductorstructure of the transducer 77. Alternatively, the second electricalconnection path can be provided via the working fluid, in which case,the working fluid is a conductive fluid.

As in the example of FIG. 1, in the apparatus 61 of FIG. 6, thesemiconductor nanowires 79 of the optical/electrical transducer 77 alsoserve as part of the wicking structure 75 for purposes of promoting theliquid flow in the phase transition cycle of the heat transfermechanism.

In addition to the semiconductor nanowire portion 79, the wickingstructure 75 includes one on more portions 81 formed on inner surfacesof the chamber wall(s) formed by the section 65 and the opticallytransmissive member 69. The portions 81 of the wicking structure formedon the section 65 and the optically transmissive member 69 could be thesame or different kinds of structures. The wicking structure in portions81 may take many forms, such as sintered metal, phosphor, glass orceramic powder; woven copper; surface grooves, mesh arrangements orsmall closely spaced wires extending inward from the surfaces of thehousing forming the walls of the chamber; as well as nano-scale wirestructures extending inward from the chamber surface(s); and variouscombinations of these forms.

In the example, however, the portions 81 formed on inner surfaces of thechamber wall formed by the section 65 and the optically transmissivemember 69 consist of nanowires formed on the appropriate surfaces. Thenanowire wicking structures on the section 65 and the opticallytransmissive member 69 may be the same, e.g. similar to one of thestructures discussed above relative to FIGS. 2 and 3. In the example ofFIG. 6, however, a first type of nanowire arrangement is provided forthe portion 81 a of the wicking structure on the metal housing section25, and a different type of nanowire arrangement is provided for theportion 81 b of the wicking structure on the optically transmissivemember 69. For example, the first type of nanowire arrangement isprovided for the portion 81 a of the wicking structure on the metalhousing section 25 may be a reflective metallic nanowire configurationas in part of the discussion of FIG. 4 above. The second type ofnanowire arrangement provided for the portion 81 b of the wickingstructure on the optically transmissive member 69 may be opticallytransmissive, although it may also contain a phosphor component forconversion of some of the light passing through the member 69 asdiscussed earlier relative to FIG. 3. Phosphor may also be provided inthe working fluid, if useful to support a particular application of thetransducer apparatus 61.

The number and size of the nanowires in the various sections 79, 81 aand 81 b would be chosen to promote the desired capillary action as wellas to achieve a degree of heat transfer appropriate for the particulartransducer design.

For purposes of discussion of a first application of a transducerapparatus 61, assume for now that the transducer apparatus 61 emitslight, e.g. the transducer 77 is a LED. A substantial portion lightemitted from the LED type transducer 77 is directed toward the opticallytransmissive member 69. As it reaches the inner surface of the opticallytransmissive member 69, some of that light excites phosphor(s) in thephosphor nanowires in the portion 81 b of the wicking structure on theoptically transmissive member 69. The excited phosphors re-emit light ofa different spectral characteristic, e.g. at a wavelength different fromthe excitation light. If provided, phosphor(s) in the working fluid maybe similarly excited to produce light of an additional spectralcharacteristic. Output light of the apparatus 61 includes a combinationof light directly emitted by the LED type transducer 77 and lightproduced by phosphor excitation. The use of phosphors may shift lightfrom a wavelength region that does not substantially contribute to theintended application into a more desirable/useful wavelength region,e.g. from ultraviolet (UV) or near UV up into the more desirable visiblepart of the spectrum. This may improve efficiency or efficacy of theoverall light output of the apparatus 61.

In the light emitting application of a transducer apparatus 61, somelight emitted by the LED type transducer 77 is directed toward the metalsection 65. If phosphors are provided in the wicking structure and/orthe working fluid, then some of the light produced by phosphorexcitation also is directed toward the metal section 65. The metal ofthe section 65 may be reflective, to redirect such light for output viathe optically transmissive member 69. However, in the example, much ofthe inner surface of the metal section 65 is covered by the portion 81 aof the wicking structure formed of reflective metallic nanowires. Hence,the metal nanowires of the portion 81 a redirect light for output viathe optically transmissive member 69.

Much like the example of FIGS. 1-3, the arrangement of FIG. 6 is alsosuitable for use in a sensor or photovoltaic application in which thetransducer 77 is a photodiode. The optical-to-electrical applicationwould function essentially in reverse of the preceding discussion of theelectrical-to-optical emitter application. For example, light enteringvia the member 69 would be processed by phosphors (if provided) and/orreflected. Then, upon impact on the photodiode type transducer 77, thelight would cause the transducer 77 to generate electricity as the lightresponsive output of the apparatus 61.

FIG. 7 is a top view, and FIG. 8 is an isometric view, of a device orlight engine for emitting light. The illustrated device 101 could beused as a light engine of a light fixture, although the exemplaryconfiguration is particularly configured for use in a lamp or ‘lightbulb,’ for example, in combination with a transparent, translucent orcolored transmissive globe (not shown).

As in the earlier examples, the light emitting device 101 may operate atany orientation, although a particular orientation is illustrated forconvenience. Some aspects of the following description of the lightemitting device 101 use directional terms corresponding to theillustrated orientation, for convenience only. Such directional termsmay help with understanding of this description of the example of FIGS.7-9 but are not intended to be limiting in any way.

The light emitting device 101 includes a light emitting transducerapparatus that is integrated with a thermal conductivity and phasetransition heat transfer mechanism, represented together as one integralelement 103 in the drawings. Heat is transferred from the apparatus 103to a heat sink 105. The heat sink 105 is formed of a highly thermallyconductive material, typically a metal such as copper or aluminum,although other materials, such as thermally conductive plastics andceramics, may be used. The heat sink 105 in our example has a core 107having a central passage, a wall of which forms a fairly tightstructural and thermal connection to the outer surface of a portion ofthe housing of the apparatus 103. The rest of the apparatus 103 extendsupward or away from the passage in the core 107 of the heat sink 105, toform a pedestal or the like with a light emitting diode at or near thedistal end. Extending radially outward from the core 107, the heat sink105 has a number of fins 109 for radiating heat to the ambientatmosphere. Straight radial fins are shown, for convenience, althoughother shapes/contours may be used, e.g. to promote heat transfer and/orto allow a desired amount of light from the emitter and phosphor to passdown between the fins.

FIG. 9A is a cross-sectional view taken along line A-A of FIG. 7, andFIG. 9B is an enlarged detail view of a portion of theoptical/electrical transducer apparatus 103 and heat sink 105corresponding to that encircled by the arrow B-B in FIG. 9A. Asillustrated, the light emitting device 101 includes a housing having asection 113 that is thermally conductive and a member 115 that is atleast partially optically transmissive. In this example, the thermallyconductive section 113 consists of a hollow copper cylinder or tubehaving a circular cross-section. A substantial portion of the coppersection 113 of the housing extends down into the passage through thecore 107 of the heat sink 105. The copper section 113 may be pressfitted into the passage or be otherwise connected and thermally coupledto the heat sink 105 in any appropriate manner suitable for efficientheat transfer and to provide structural support that may be necessaryfor the apparatus 103. The end of the copper cylinder or tube of section113 opposite the optically transmissive member 115 is closed, e.g. by aflat circular section of copper.

In this example, the optically transmissive member 115 consists of ahollow glass cylinder or tube having a circular cross-section and closedat one end by a curved or dome-shaped section of the glass. Thecylindrical thermally conductive section 113 and the opticallytransmissive member 115 have approximately the same lateral dimensionsso as to form a relatively straight continuous cylinder, although otherlateral and cross-sectional shapes could be used. For example, one orboth of the elements 113, 115 could vary in shape and/or dimension alongthe lateral length of the light emitting transducer apparatus 103, e.g.so that the region away from the heat sink 105 is somewhat enlarged orbulbous at the end of the pedestal. Also, the distal end of theoptically transmissive member 115 (furthest away from the heat sink 105)could have other shapes, e.g. to be flat or concave instead of theillustrated dome shape.

The glass optically transmissive member 115 is connected to the copperthermally conductive section 113 of the light emitting transducerapparatus 103 to form a housing enclosing a vapor chamber and asemiconductor light emitting device. Specifically, the section 113 andmember 115 are connected so as to form a vapor tight seal for thechamber. The two elements may be joined by a glass frit process or byapplication of a suitable epoxy, at the glass/copper interface.

Glass and copper are given by way of examples of the materials of theoptically transmissive member 115 and the thermally conductive section113. Those skilled in the art will appreciate that other opticallytransmissive materials and thermally conductive materials may be used.

The semiconductor light emitting device in this example includessemiconductor nanowires forming a light emitting diode (LED) 117, withinthe chamber. In this example, the semiconductor nanowires forming theLED 117 are formed or mounted on the curved interior surface at thedistal end of the optically transmissive member 115. The structure ofthe LED 117 with the nanowires may be similar to the transducer devicediscussed above relative to FIG. 2. As noted at one point in thediscussion of FIG. 2, reflectors may be provided at the distal (innermost) ends of the nanowires of the LED device 117, to increase output oflight from the LED through the dome of the glass member 115. Since theLED 117 is mounted on glass, one or both electrical connections to theLED may be provided by separate leads (two of which are shown in thedrawing), in which case, the working fluid need not be conductive.

The glass forming the optically transmissive member 115 may betransparent or translucent or exhibit other transmissive characteristics(e.g. non-white color filtering), depending on the application for thedevice 101. The glass of the member 115 permits emission of at leastsome light from the LED 117 as an output of the light emitting device101.

For purposes of operating as a thermal conductivity and phase transitionheat transfer mechanism, the light emitting device 101 also includes aworking fluid within the chamber. The working fluid directly contactsthe outer surfaces of the nanowires of the LED 117. The pressure withinthe chamber configures the working fluid to absorb heat from the LED117, particularly from the nanowires, during operation of the device101. The fluid vaporizes at a relatively hot location at or near thesemiconductor nanowires of the LED 117 as the working fluid absorbsheat. The vapor transfers heat to and condenses at a relatively coldlocation of the copper section 113 in contact with the heat sink 105,and the condensed working fluid returns as a liquid to the relativelyhot location at or around the LED 117.

As in the earlier examples, the device 101 of FIG. 7 includes a wickingstructure mounted within the chamber to facilitate flow of condensedliquid of the working fluid from the cold location to the hot location.Together, the housing, the chamber, the working fluid and the wickingstructure form a thermal conductivity and phase transition heat transfermechanism for transferring heat away from the LED 117, in this case, tothe heat sink 105. The semiconductor nanowires of LED 117 on the innercurved surface of the glass member 115 are configured to serve as aportion of the wicking structure.

In addition to the nanowires of the LED 117, the wicking structureincludes a non-LED (not semiconductor nanowires) wick 121 formed on theportions of the inner surface of the glass member 115 in regions otherthan the region(s) covered by the structure of the LED 117. The overallwicking structure further includes a non-LED (not semiconductornanowires) wick 123 on the inner surface of the copper section 113. Thewicks 121 and 123 may take many forms, such as sintered metal, phosphor,glass or ceramic powder; woven copper; surface grooves, mesharrangements or small closely spaced wires extending inward from thesurfaces of the housing forming the walls of the chamber; as well asnano-scale wire structures extending inward from the chamber surface(s);and various combinations of these forms. The wicks may be similar toeach other or different, e.g. as discussed above relative to the exampleof FIG. 6. In the example of FIGS. 7-9, the wick in the glass member 115may be formed of a material that is at least somewhat opticallytransmissive, whereas the wick in the copper section 113 may be at leastsomewhat reflective.

Depending on the application of the light emitting device 101 and/or thelight output properties of the LED, the device 101 may or may notinclude a phosphor or other luminescent material. In the presentexample, however, the light emitting device 101 does include a phosphor.As outlined earlier, the phosphor may be provided in some or all of thewicking structure. In the example of FIGS. 9A and 9B, the phosphor isprovided in the form of a layer 125 between the LED 117 and the curvedinterior surface at the distal end of the optically transmissive member115 on which the LED is mounted. Light emerging from the LED 117 towardthe curved interior surface of the optically transmissive member 115passes through the phosphor layer 125. Some of the light excites thephosphor, and the excited phosphor converts optical energy from the LED117 from energy in one wavelength range (the excitation band of thephosphor) to another wavelength range. For example, the phosphor 125 mayconvert some energy from the LED 117 from a less desirable wavelengthrange (e.g. near or outside the visible spectrum) to a more desirablewavelength range (e.g. to fill-in a gap in the spectral characteristicof light produced by the emitter), to improve efficiency of the lightemitting device 101 and/or to improve the quality of the light output.

The phosphor layer may include one type of phosphor or phosphor of anumber of types, depending on the desired characteristics of the lightoutput of the device 101. Also, the phosphor layer may extend down theinner surface of the housing, e.g. down the inner cylindrical surface ofthe glass member 115 to the glass/copper interface. Additional phosphormay be provided in the working fluid.

FIG. 10 is a top view, and FIG. 11 is an isometric view of anotherdevice or light engine 101′ for emitting light. FIG. 12A is a crosssection view taken along line A-A of FIG. 10, and FIG. 12B is anenlarged detail view of a portion of the optical/electrical transducerapparatus and heat sink of FIG. 12A, showing the addition of a phosphorlayer. The device or light engine 101′ is generally similar to thedevice 101 of FIGS. 7-9, like reference numerals identify correspondingelements, and the discussion above can be referenced for detailedinformation about the corresponding elements. The device 101′ doesinclude a phosphor. However, instead of including the phosphor as alayer between the light emitting diode and the surface of the opticallytransmissive member 115, the phosphor in the device 101′ is carried bythe working fluid 125′. A phosphor bearing working fluid as may be usedin the device 101′ has been discussed earlier with regard to theexamples of FIGS. 3 and 4.

FIGS. 7-12 and the descriptions thereof relate to light emitting devices101, 101′. The present teachings are also applicable to transducers thatconvert optical energy into electrical energy. To appreciate suchadditional applicability, it may be helpful to consider a specificexample of an optical-to-electrical transducer, with reference to FIGS.13-15.

FIG. 13 is a top view, and FIG. 14 is an isometric view, of a device 131for producing an electrical signal in response to light. The device 131may be configured as an optical energy sensor or detector, e.g. for UV,visible light, infrared, or the like; and/or the device 131 may beconfigured as a photovoltaic device for generating power in response tooptical energy in a desired spectral range. Although not shown, anoptically transmissive outer element such as a globe may be added as acover or the like.

As in the earlier examples, the light responsive transducer device 131may operate at any orientation, although a particular orientation isillustrated for convenience. Some aspects of the following descriptionof the light transducer device 131 use directional terms correspondingto the illustrated orientation, for convenience only. Such directionalterms may help with understanding of this description of the example ofFIGS. 13-15 but are not intended to be limiting in any way.

The device 131 includes a light responsive transducer apparatus(including the actual semiconductor transducer, such as a photodiode)that is integrated with a thermal conductivity and phase transition heattransfer mechanism, represented together as one integral element 133 inthe drawings. Heat is transferred from the apparatus 133 to a heat sink135. The heat sink 135 is formed of a highly thermally conductivematerial, typically a metal such as copper or aluminum, although othermaterials, such as thermally conductive plastics and ceramics, may beused. The heat sink 135 in our example has a core 137 having a centralpassage, a wall of which forms a fairly tight structural and thermalconnection to the outer surface of a portion of the housing of theapparatus 133. The rest of the apparatus 133 extends upward or away fromthe passage in the core 137 of the heat sink 135, to form a pedestal orthe like with the photodiode or the like at or near the distal end.Extending radially outward from the core 137, the heat sink 135 has anumber of fins 139 for radiating heat to the ambient atmosphere.

FIG. 15A is a cross-sectional view taken along line A-A of FIG. 13, andFIG. 15B is an enlarged detail view of a portion of theoptical/electrical transducer apparatus 133 and heat sink 135corresponding to that encircled by the arrow B-B in FIG. 15A. Asillustrated, the light responsive transducer device 131 includes ahousing having a section 143 that is thermally conductive and a member145 that is at least partially optically transmissive.

In the example of FIGS. 15A, 15B, the member 145 is a curved glasselement having an inwardly reflective outer surface to form a reflectorwith respect to the transducer. Various curvatures may be used toconcentrate incoming light at the location of the actual semiconductortransducer 147. Reflectivity can be provided by a coating or othersurface treatment at the curved outer surface of the glass member 145 orpossibly by total internal reflection of a substantial portion of theincident light.

A separate member could be used as the optically transmissive member asin the examples of FIGS. 7-12 and as shown in the FIG. 14. In such acase, the reflector would be fitted over the glass member, and thereflector may be solid as shown or may be an open reflector. However,the reflector is omitted from the isometric view of FIG. 14, forconvenience, to more clearly show the portion of the apparatus 133extending above the heat sink 135.

In the examples of FIGS. 15A, 15B with the solid reflector 145, ahollowed portion of the glass forms a portion of the housing of thetransducer apparatus 133 with the integral thermal conductivity andphase transition heat transfer mechanism. Stated another way, in thisexample, the glass of the reflector 145 also serves as the opticallytransmissive member of the housing. It should be noted that the detailview of FIG. 15B represents only the portion of the reflector/member 145encircled by the arrow B-B and does not show the entire reflector 145(compare to FIG. 15A).

The thermally conductive section 143 consists of a hollow coppercylinder or tube having a circular cross-section. A substantial portionof the copper section 143 of the housing extends down into the passagethrough the core 137 of the heat sink 135. The copper section 143 may bepress fitted into the passage or be otherwise connected and thermallycoupled to the heat sink 135 in any appropriate manner suitable forefficient heat transfer and to provide structural support that may benecessary for the apparatus 133. The end of the copper cylinder or tubeof section 143 opposite the optically transmissive member 145 is closed,e.g. by a flat circular section of copper.

In this example, the optically transmissive member 145 consists of ahollow cylinder or tube formed within the glass of the reflector 145.The hollow section has a circular cross-section and is closed at one endby a curved or dome-shaped contour within the glass. The interior of thecylindrical thermally conductive section 143 and the hollow within theoptically transmissive member/reflector 145 have approximately the samelateral dimensions so as to form a relatively straight continuouscylindrical volume for the vapor chamber within the housing. As in theexamples of FIGS. 7-12, other lateral and longitudinal shapes may beused for either or both of the section 143 and the interior volume ofthe glass member 145.

The glass optically transmissive member 145 is connected to the copperthermally conductive section 143 of the light emitting transducerapparatus 133 to form a housing enclosing a vapor chamber and a lightresponsive semiconductor transducer. Specifically, the section 143 andmember 143 are connected so as to form a vapor tight seal for thechamber. The two elements may be joined by a glass frit process or byapplication of a suitable epoxy, at the glass/copper interface.

Glass and copper are given by way of examples of the materials of theoptically transmissive member 145 and the thermally conductive section143. Those skilled in the art will appreciate that other opticallytransmissive materials and thermally conductive materials may be used.

The apparatus 133 includes a semiconductor transducer that generates anelectrical signal in response to light. As shown at 147, thesemiconductor transducer is formed so as to include semiconductornanowires. The semiconductor transducer may take and of a number ofdifferent forms, although for purposes of further discussion, we willassume that the semiconductor transducer 147 is configured as aphotovoltaic or the like.

The glass forming the optically transmissive portion of the reflector145 may be transparent or translucent or exhibit other transmissivecharacteristics (e.g. non-white color filtering), depending on thephotovoltaic or sensor application for the device 131. The glass of themember 145 permits light directed toward the reflector/member to passthrough to the photo voltaic device 147 as an input of the lightresponsive transducer device 131. Light impacting on the reflectiveportion of the member 145 is reflected back through the glass forconcentration at the position of the photovoltaic 147.

As discussed above, the device 131 includes a housing having a section143 that is thermally conductive and a member 145 that is at leastpartially optically transmissive; and together, the housing section 143and the optically transmissive member form a vapor chamber containingthe working fluid for the integral thermal conductivity and phasetransition heat transfer mechanism.

In this example, the semiconductor nanowires forming the photovoltaic147 are formed or mounted on the curved interior surface at the distalend of the cavity within the optically transmissive member 145. Thestructure of the photovoltaic 147 with the nanowires may be similar tothe transducer device discussed above relative to FIG. 2. As noted inearlier discussions, reflectors may be provided at distal ends of thenanowires, in this case to reduce the amount of light that escapes pastthe photovoltaic into the rest of the chamber and thus increase theamount of light processed by the photovoltaic 147. Since thephotovoltaic 147 is mounted on glass, one or both electrical connectionsto the photovoltaic may be provided by separate leads (two of which areshown in the drawing), in which case, the working fluid need not beconductive.

For purposes of operating as a thermal conductivity and phase transitionheat transfer mechanism, the light emitting device 131 also includes aworking fluid within the chamber. The working fluid directly contactsthe outer surfaces of the nanowires of the photovoltaic 147. Thepressure within the chamber configures the working fluid to absorb heatfrom the photovoltaic, particularly from the nanowires, during operationof the device 131, to vaporize at a relatively hot location at or nearthe semiconductor nanowires of the photovoltaic 147 as the working fluidabsorbs heat. The vapor transfers heat to and condenses at a relativelycold location of the copper section 143 in contact with the heat sink135, and the condensed working fluid returns as a liquid to therelatively hot location at or around the photovoltaic 147.

As in the earlier examples, the device 131 of FIGS. 13-15 includes awicking structure mounted within the chamber to facilitate flow ofcondensed liquid of the working fluid from the cold location to the hotlocation. Together, the housing, the chamber, the working fluid and thewicking structure form a thermal conductivity and phase transition heattransfer mechanism for transferring heat away from the photovoltaic 147.The semiconductor nanowires of photovoltaic 147 on the inner curvedsurface of the glass member 145 are configured to serve as a portion ofthe wicking structure.

In addition to the nanowires of the photovoltaic 147, the wickingstructure includes a wick 151 formed of non-semiconductor nanowires onthe portions of the inner surface of the glass member 145 in regionsother than the region(s) covered by the structure of the photovoltaic147. The overall wicking structure further includes a wick 153 formed ofnon-semiconductor nanowires on the inner surface of the copper section143. Although formed of nanowires in the example, the wicks 151 and 153may take many forms, such as sintered metal, phosphor, glass or ceramicpowder; woven copper; surface grooves, mesh arrangements or smallclosely spaced wires extending inward from the surfaces of the housingforming the walls of the chamber; as well as nano-scale wire structuresextending inward from the chamber surface(s); and various combinationsof these forms. The wicks may be similar to each other or different,e.g. as discussed above relative to the earlier examples. In the exampleof FIGS. 13-15, the wick in the glass member 145 may be formed of amaterial that is at least somewhat optically transmissive, whereas thewick in the copper section 143 may be at least somewhat reflective.

The example of FIGS. 13-15 does not include a phosphor. However, somesensor or photovoltaic applications of the apparatus 131 may include aphosphor. If useful, a phosphor appropriate to the application could beincluded in any of the various ways discussed above with regard toearlier examples.

Those skilled in the art will appreciate that the teachings above may beapplied in a variety of different ways and are not limited to thespecific structures, materials and arrangements shown in the drawingsand described above. For example, the instructed devices include onetransducer with the nanowires forming part of the wick within thechamber of the thermal conductivity and phase transition heat transfermechanism. It is contemplated that a single device or apparatus mayinclude multiple transducers with the nanowires of the transducersforming part of the wick. In a device having multiple semiconductortransducers, the transducers may be substantially similar, e.g. to emitor sense the same type of light. Alternatively, different transducers inone device may serve multiple purposes. For example, one semiconductortransducer might be configured to sense or emit light of a firstspectral characteristic, whereas another semiconductor transducer mightbe configured to sense or emit light of a different second spectralcharacteristic. In another example of a multi-transducer arrangement,one semiconductor transducer might be configured to sense or emit lightand another semiconductor transducer might be configured as a sensor oflight or temperature.

It should be apparent from the discussion above that when an element isreferred to as being “on”, “attached” to, “connected” to, “coupled”with, “contacting,” etc., another element, it can be directly on,attached to, connected to, coupled with or contacting the other elementor intervening elements or spacing may also be present. In contrast,when an element is referred to as being, for example, “directly on”,“directly attached” to, “directly connected” to, “directly coupled” withor “directly contacting” another element, there are no interveningelements present, although in some cases there may be interveningelements or layers of up to a micron or so, so long as such layers orelements do no substantially reduce thermal conductivity. It will alsobe appreciated by those of skill in the art that references to astructure or feature that is disposed “adjacent” another feature mayhave portions that are nearby or even overlap or underlie the adjacentfeature.

Similarly, spatially relative terms, such as “under,” “below,” “lower,”“over,” “upper” related orientation or directional terms and the like,that may have been used above for ease of description to describe oneelement or feature's relationship to another element(s) or feature(s)orientation or direction as illustrated in the figures. It will beunderstood that the spatially relative terms are intended to encompassdifferent orientations of the device in use or operation in addition tothe orientation depicted in the figures. For example, if the device inthe figures is inverted, elements described as “under” or “beneath”other elements or features would then be oriented “over” the otherelements or features.

While the foregoing has described what are considered to be the bestmode and/or other examples, it is understood that various modificationsmay be made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that the teachings may beapplied in numerous applications, only some of which have been describedherein. It is intended by the following claims to claim any and allapplications, modifications and variations that fall within the truescope of the present teachings.

What is claimed is:
 1. An optical/electrical transducer apparatus,comprising: a housing having a section that is thermally conductive anda member that is at least partially optically transmissive, theoptically transmissive member being connected to the thermallyconductive section of the housing to form a seal for a vapor tightchamber; a working fluid within the chamber, wherein pressure within thechamber configures the working fluid to absorb heat during operation ofthe apparatus, to vaporize at a relatively hot location as the workingfluid absorbs heat, to transfer heat to and condense at a relativelycold location, and to return as a liquid to the relatively hot location;and a wicking structure in contact with the working fluid comprisingsemiconductor nanowires within the chamber configured as an activedriven part of an optical/electrical transducer and configured to bedriven to emit light from within the chamber through or to be driven bylight received in the chamber via the optically transmissive member. 2.The apparatus of claim 1, further comprising a wick other thansemiconductor nanowires.
 3. The apparatus of claim 2, wherein the otherwick is at least partially reflective.
 4. The apparatus of claim 2,wherein the other wick comprises metallic nanowires.
 5. The apparatus ofclaim 1, wherein the semiconductor nanowires are configured as at leastpart of an electrical-to-optical type transducer, for emitting light viathe optically transmissive member of the housing when driven by anelectrical current.
 6. The apparatus of claim 1, wherein thesemiconductor nanowires are configured as at least part of anoptical-to-electrical type transducer, for producing an electricalcurrent in response to light received via the optically transmissivemember of the housing.
 7. The apparatus of claim 1, wherein the workingfluid is electrically conductive for carrying an electrical current toor from at least some of the semiconductor nanowires.
 8. The apparatusof claim 1, wherein the housing, the chamber and the working fluidtogether form a thermal conductivity and phase transition heat transfermechanism for transferring heat away from the optical/electricaltransducer within the chamber.
 9. The apparatus of claim 1, wherein eachsemiconductor nanowire comprises: a first semiconductor of one of twosemiconductor types, the first semiconductor forming a core electricallycoupled to a conducting base; a second semiconductor of the other of thetwo semiconductor types, the second semiconductor being exposed to theworking fluid in the chamber; and a semiconductor junction or intrinsicregion formed between the first and second semiconductors.
 10. Anoptical/electrical transducer apparatus, comprising: a semiconductortransducer including semiconductor nanowires configured to be driven toconvert between optical and electrical energy; a housing having asection that is thermally conductive and a member, that is at leastpartially optically transmissive, the optically transmissive memberbeing connected to the thermally conductive section of the housing toform a seal for a vapor tight chamber formed by the housing, thesemiconductor transducer being mounted with at least the semiconductornanowires within the chamber and configured so as to be driven to emitlight from within the chamber or to receive light to drive thesemiconductor nanowires in the chamber, via the optically transmissivemember; and a working fluid within the chamber, wherein pressure withinthe chamber configures the working fluid to absorb heat from thesemiconductor transducer during operation of the apparatus, to vaporizeat a relatively hot location at or near the semiconductor nanowires asthe working fluid absorbs heat, to transfer heat to and condense at arelatively cold location, and to return as a liquid to the relativelyhot location.
 11. The apparatus of claim 10, wherein the transducerhaving the semiconductor nanowires is configured as anelectrical-to-optical transducer for emitting light when driven by anelectrical current.
 12. The apparatus of claim 10, wherein thetransducer having the semiconductor nanowires is configured as anoptical-to-electrical transducer for producing an electrical current inresponse to light.
 13. The apparatus of claim 10, wherein the workingfluid is electrically conductive for carrying an electrical current toor from at least some of the semiconductor nanowires.
 14. The apparatusof claim 10, wherein the housing, the chamber and the working fluidtogether form a thermal conductivity and phase transition heat transfermechanism for transferring heat away from the semiconductor transducer.15. The apparatus of claim 10, wherein each semiconductor nanowirecomprises: a first semiconductor of one of two semiconductor types, thefirst semiconductor forming a core electrically coupled to a conductingbase; a second semiconductor of the other of the two semiconductortypes, the second semiconductor being exposed to the working fluid inthe chamber; and a semiconductor junction or intrinsic region formedbetween the first and second semiconductors.
 16. An optical/electricaltransducer apparatus, comprising: a housing having a section that isthermally conductive and a member that is at least partially opticallytransmissive, the optically transmissive member being connected to thethermally conductive section of the housing to form a seal for a vaportight chamber; a working fluid within the chamber, wherein pressurewithin the chamber configures the working fluid to absorb heat duringoperation of the apparatus, to vaporize at a relatively hot location asthe working fluid absorbs heat, to transfer heat to and condense at arelatively cold location, and to return as a liquid to the relativelyhot location; and semiconductor nanowires, mounted within the chamber,configured to be in contact with the working fluid and to operateelectrically as at least part of an active optical/electrical transducerto convert between optical and electrical energy, the semiconductornanowires being positioned to be driven to emit light from inside thechamber through or to be driven by light received in the chamber via theoptically transmissive member when operating as part of theoptical/electrical transducer.
 17. The apparatus of claim 16, whereinthe semiconductor nanowires are configured to operate as anelectrical-to-optical transducer for emitting light when driven by anelectrical current.
 18. The apparatus of claim 16, wherein thesemiconductor nanowires are configured to operate as anoptical-to-electrical transducer for producing an electrical current inresponse to light.
 19. The apparatus of claim 16, wherein the housing,the chamber and the working fluid together form a thermal conductivityand phase transition heat transfer mechanism for transferring heat awayfrom the semiconductor transducer.
 20. The apparatus of claim 16,wherein each semiconductor nanowire comprises: a first semiconductor ofone of two semiconductor types, the first semiconductor forming a coreelectrically coupled to a conducting base; a second semiconductor of theother of the two semiconductor types, the second semiconductor beingexposed to the working fluid in the chamber; and a semiconductorjunction or intrinsic region formed between the first and secondsemiconductors.